def f(t):
    time=0
    X=0
    for i in range(N-t):
        X+=abs(A[i]-A[i+t])
        time+=1
    return X/time
#==================================================
from math import floor,ceil

N=int(input())
A=list(map(int,input().split()))

T={"C4":261.6, "D4":294.3, "E4":327.0, "F4":348.8, "G4":392.4, "A4":436.0, "B4":490.5}

beta=float("inf")
ans=""
for p in T:
    alpha=min(f(floor(N/T[p])), f(ceil(N/T[p])))
    if beta>alpha:
        beta=alpha
        ans=p

print(ans)